The present invention relates to wireless communication devices that use polar modulation to transmit information.
Some wireless communication devices communicate by modulating the polar components (e.g., amplitude and phase) of a radio carrier. For example, a phase modulation signal and an amplitude modulation signal may be generated at a baseband frequency. The phase modulation signal may then be used to modulate the phase of an RF carrier that has a constant envelope amplitude. The phase modulated RF carrier may then be passed through a power amplifier whose supply voltage is modulated by the amplitude modulation signal to generate the envelope of a desired output signal.
Unexpected delay between the phase modulation signal and the amplitude modulation signal may cause the signals to be applied to different portions of the RF carrier, and may result in undesirable distortion of the output signal. Moreover, the amplitude modulation may cause inadvertent phase modulation due to undesired feedback between phase modulation components and amplitude modulation components.